Abrasive tape and method of producing the same

ABSTRACT

For producing an abrasive tape (11) including a film substrate (2) and a polishing abrasive layer (10) laminated on one surface of the film substrate (2) and having on the outer surface thereof a plurality of recessed parts (9), the film substrate (2) is wrapped partially around the outer peripheral surface of a roll formplate (1) having on the surface thereof a plurality of concavities (5), and, as the roll formplate (1) is rotated, the film substrate (2) is fed thereto. On one hand, an ionizing radiation curing type resin (3) is supplied into the interface between the roll formplate (1) and the film substrate (2) therearound to be formed by the concavities (5), and the recessed parts (9) are formed on the resin surface. During this forming, radiation rays (R) are projected from an ionizing radiation ray source (8) toward the resin (3) thereby to cure the resin (3) and, at the same time, to render the resin (3) and the film substrate (2) into an integral structure. The abrasive tape (11) obtained in this manner is separated from the roll formplate (1). The abrasive tape (11) thus obtained is of high product quality. The production method is highly efficient and is suitable for mass production of abrasive tapes of identical concave-convex surface figuration.

This is a division of application Ser. No. 08/379,459 filed Mar. 22,1995, now U.S. Pat. No. 5,709,598.

TECHNICAL FIELD

The present invention relates to an abrasive tape for finish lapping orpolishing with high precision to a mirror-surface finish such surfacesas those of floppy disks, magnetic heads, precision electroniccomponents, and end surfaces of optical fibers. The invention relatesalso to a method of producing the abrasive tape.

BACKGROUND ART

As abrasive tapes of the above stated kind, in general, there are thoseof a structural organization wherein, on a substrate material, a coatingcomprising a polishing abrasive material and a binder component isapplied to form a polishing film. An abrasive tape of this character hasa simple structural organization and can be readily produced. During itsuse, however, debris formed from the workpiece being polished tends toinfiltrate between the abrasive polishing film of the abrasive tape andthe workpiece. If the polishing process is continued in this state, thesurface of the workpiece will be damaged by this polishing debris, orthe polishing debris will adhere to the film surface and cause its poresor recesses to become clogged. As a result, the polishing capacity ofthe abrasive tape has dropped considerably heretofore.

Furthermore, an abrasive tape provided with grooves in its polishinglayer has been proposed. In the process of forming the polishing layerof this tape, a paint containing a large quantity of an inorganicingredient in a coating compound is applied. Then the concavities andconvexities of the Bernard cell due a "convection cell phenomenon" whichoccurs in the coating layer at the time when the solvent is dried areutilized as groove forms of the polishing layer. (Reference: JapanesePat. Laid-Open Publn. No. 62-255069.) In the case of this abrasive tape,however, the shape as viewed in plan view of the grooved parts thusformed becomes restricted to an approximately hexagonal shape forreasons due to the production method. Moreover, it has been difficult toform recesses consistently of the same pattern, and products of stablequality could not be easily obtained. Furthermore, the control ofconditions such as the composition of the solvent of the coatingmaterial for forming the polishing layer, the coating quantity, and thedrying conditions in the production process for uniformity andstabilization of the pattern of the grooved parts to be thus formed hasbeen difficult. Consequently, there has been the problem of extremelycomplicated production procedures. Furthermore, the concavities andconvexities that can be formed on this abrasive tape is limited, interms of the number of the polishing abrasive, to between #6,000 and#7,000 measured according to JIS R 6001. Polishing abrasives of numbershigher than this (i.e., concavities and convexities of dimensions lessthan this) could not be obtained.

Furthermore, in the method described in the above mentioned JapanesePat. Laid-Open Publn. No. 62-255069 and other known methods (JapaneseUtility Model Laid-Open Publn. Nos. 55-89564 and 59-39168), the formingof polishing layers into concave-convex pattern forms by using aprinting process such as gravure printing and screen printing isdisclosed. Furthermore, in Japanese Pat. Laid-Open Publn. No. 2-83172,the forming of a concave/convex pattern by applying a coating of a resinliquid in which polishing abrasive particles have been dispersed on afilm substrate and laminating thereon by pressing a film for impartingconcavities/convexities is disclosed. By this method, it has not beenpossible to prevent completely the formation of projections ofindependent polishing abrasive material on the surface of the polishinglayer thus obtained. When such projections are present, the workpieceundergoing polishing is damaged by scratching or scoring. Thus thismethod becomes unsuitable especially for polishing requiring precision.

Furthermore, because of friction between the abrasive tape and theworkpiece being polished, the abrasive tape and the workpiece becomeelectrostatically charged at the time of polishing. For this reason theremoval of polishing debris from the polished parts becomes difficult,and residual polishing debris becomes entrapped between the abrasivetape and the workpiece, whereby scratch damage occurs, or dust in theair or polishing debris is adsorbed on the surface after polishing andmust be subsequently cleaned off.

Furthermore, depending on the conditions, sparking may occur between theabrasive tape and the workpiece and damage the surface of the workpiecein some cases.

Accordingly, it is an object of the present invention to obtain anabrasive tape of high quality which is capable of solving the abovedescribed problems of the prior art.

It is another object of this invention to obtain a novel method by whichthe above described abrasive tape can be stably produced.

DISCLOSURE OF THE INVENTION

The abrasive tape according to the present invention is characterized inthat, in an abrasive tape having a film substrate and an abrasivepolishing layer laminated on one surface of the substrate, the polishinglayer has on the outer surface thereof a plurality of mutually isolatedbut adjoining recessed parts each demarcated by being encompassed aroundthe peripheral border thereof by embankment-like convexities.

Furthermore, in the method according to this invention of producing anabrasive tape comprising a film substrate and a polishing layerlaminated on one surface thereof and having a plurality of recesses: aformplate having a plurality of concavities for forming said recesses isprepared; of the surface and concavities of this formplate, at least theconcavities are filled with a resin of ionizing radiation curing type;the film substrate is caused to contact this ionizing radiation curingtype resin; while the film substrate is contacting the ionizingradiation curing type resin, said resin is irradiated with ionizingradiation rays; thus, the resin interposed between the film substrateand the formplate is cured thereby to bond together said resin and thefilm substrate; and the film substrate and the polishing layer of thecured resin adhering securely thereto and provided with a shape which iscomplementary to that of the aforementioned concavities are peeled offthe aforementioned formplate thereby to obtain an abrasive tape. Thusthe abrasive tape is obtained.

According to this invention, an abrasive tape having a polishing layerin which recessed parts that have been formed constantly with faithfulreplication with respect to the plate concavities of the formplate andwith extreme sharpness can be produced. Furthermore, in comparison withthe case of forming the recessed parts of the polishing layer by, forexample, the thermo-embossing process or the method of using a film forstamping, a high quality product in which the shape of the recessedparts obtained are sharp and exactly as desired can be readily produced.Furthermore, the production process itself is not complicated but issimple and convenient, whereby mass production of stable product qualityand high efficiency becomes possible.

According to a desirable mode of practice of the abrasive tape of thisinvention, the polishing layer comprises a binder of a crosslinked typeresin and particles of a polishing material or abrasive grains dispersedtherein, and the density of the polishing material particles or grainscan be made to increase progressively from the film substrate side tothe side of the polishing layer outer surface. By so doing, thedistributed density of the polishing material particles or grains, incomparison with that in known polishing tapes which it is substantiallyuniform from the polishing layer surface to the back surface, is suchthat the polishing material particle density of the outer surface ishigher even with the same added quantity of the polishing material,whereby the polishing capability can be made higher. Furthermore, sincethe polishing material particles or grains are bonded strongly by thebinder of the three-dimensionally crosslinked, ionizing radiation curingtype resin, they cannot be easily separated off during polishing.Furthermore, even if the outer layer of the polishing layer isrelatively brittle, the bottom layer parts have a lower densities of thepolishing material particles or grains and therefore have relativelymore flexibility and have toughness. For this reason, the strength ofthe polishing layer as a whole is secured. Furthermore, since thestresses of the outer layer are absorbed by the bottom layers, even ifthe polishing layer as a whole is bent or used in a polishing process,it will not fracture or the polishing particles or grains will notseparate off.

Furthermore, according to another desirable mode of practice of theabrasive tape of this invention, the polishing layer comprises a binderof a crosslinked type resin and polishing material particles or abrasivegrains dispersed therein. Within the three-dimensional network molecularstructure of said crosslinked type resin, surface-active agent moleculescan be caused to be contained in a state wherein they are chemicallycombined within said network molecular structure. By this constitutionalarrangement, such occurrences as electrostatic charging of the polishinglayer during polishing thereby causing adsorption of polishing debrisand dust on the polishing layer, contamination of the article beingpolished, electrical discharging, and scratching or scoring of thearticle being polished by adsorbed debris, etc., cannot occur. In thisconnection, there is little possibility of adhesion of the surfaceactive agent or deterioration of the antistatic effect.

Still furthermore, according to a desirable mode of practice of theabrasive tape production method of this invention, the irradiation forcomplete setting of the binder of the polishing layer is carried out bydividing the irradiation quantity or dosage into two or more doses,whereby the crosslinking curing reaction proceeds by degrees of two ormore steps to completion, and in each step of this process, at least onepart of the polishing material particles or grains is caused to migrategradually from the film substrate side to the side of the roll formplatesurface. In this connection, moreover, said multistep curing reactioncan be carried out in the space or interface confined between the rigidsurface of the roll formplate and the film substrate. By this procedure,the outer surface of the polishing layer of the abrasive tape thusobtained will not have outwardly protruding particles, and in addition,even with the same quantity of addition of polishing material, a higherpolishing performance can be attained and embrittlement of the polishinglayer does not occur in comparison with the case of products obtained bymethods known in the prior art.

Furthermore, by the abrasive tape production method of this invention, apolishing layer can be obtained by: dividing the irradiation quantityfor fully curing the polishing layer into a plurality of steps; firstirradiating that portion of the total irradiation quantity from thefirst step to an intermediate step through the ionizing radiation curingtype resin liquid during the period wherein the film substrate iscontacting the roll formplate; permitting the incompletely set resinlayer to set to a degree whereby it can be separated from the formplate;then separating the film substrate, together with the incompletely curedresin layer which has been formed with recessed parts, from the rollformplate; and thereafter irradiating the portion of the irradiationquantity of the remaining steps from the side of the incompletely curedresin layer thereby to complete the curing of the ionizing radiationcuring type resin layer. By carrying out this process, a polishing layerin which the layer surface has a high crosslinked density and a highdegree of hardness, yet ample flexibility being retained, and defectssuch as cracks, fissures, and separation of the polishing materialparticles or grains cannot easily occur is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view for describing the fundamental principle of the methodof producing the abrasive tape according to the present invention;

FIG. 2 is a partial sectional view of an abrasive tape obtained by themethod of FIG. 1;

FIG. 3 is a partial perspective view of the abrasive tape of FIG. 2;

FIG. 4 is a sectional view showing one example of concave parts of aroll formplate;

FIG. 5 is a sectional view showing another example of concave parts of aroll formplate;

FIGS. 6 through 10 are views sequentially indicating the process stepsfor forming concave parts of a roll formplate;

FIG. 11 is a graph indicating a curve of cumulative frequencydistribution of surface roughness of a roll formplate;

FIGS. 12 through 14 are sectional views respectively showing variousshapes of concave parts of roll formplates;

FIGS. 15A, 16A, 17A, 18A, 19A, and 20A are graphs respectivelyindicating various examples of cumulative frequency distributions ofdepths of concave parts of roll formplates;

FIGS. 15B, 16B, 17B, 18B, 19B, and 20B are sectional views showingshapes of various different concave parts of roll formplatecorresponding respectively to the curves of the graphs of FIGS. 15A,16A, 17A, 18A, 19A, and 20A;

FIGS. 21 through 25 are partial perspective views respectively showingvarious different examples of concave/convex shapes of surfaces ofpolishing layers of abrasive tapes;

FIG. 26 is an enlarged sectional view indicating a state of polishing ofan article by an abrasive tape;

FIG. 27 is a sectional view showing the state of entry of polishingdebris into recessed parts of a polishing layer of an abrasive tape atthe time of polishing;

FIG. 28 is a view for describing another example of the method ofproducing an abrasive tape according to this invention;

FIG. 29 is an explanatory view showing still another example of theabrasive tape production method according to the invention;

FIG. 30 is a partial view from the left of FIG. 29;

FIGS. 31 through 33 are enlarged sectional views indicating successivesteps in the process of forming the polishing layer of an abrasive tape;

FIGS. 34 through 37 are enlarged sectional views indicating successivelythe steps of another process of forming the polishing layer of anabrasive tape;

FIG. 38 is an enlarged sectional view indicating an undesirable stateoccurring in a polishing layer;

FIG. 39 is a diagram indicating an example of a desirable positionallayout of apparatus for irradiating a roll formplate with radiationrays; and

FIGS. 40 and 41 are diagrams respectively indicating different examplesof positional layouts of apparatus for irradiation with radiation rays.

BEST MODES FOR CARRYING OUT THE INVENTION

FIG. 1 is a view for describing a process indicating one example ofpractice of the production method of the present invention. In thefigure, 1 is a roll formplate (intaglio printing plate). Around theperipheral surface of this roll formplate 1, a film substrate 2 ispartially wrapped and is fed in the arrow direction. Below the rollformplate 1, a pan 4 containing an ionizing radiation curable resincontaining an abrasive material is provided.

According to the present invention, plate concavities 5 having a shapefor imparting shapes of recessed parts to the polishing layer of theabrasive tape are formed on the outer surface of the roll formplate 1.The film substrate 2 is sent from a supply roll 2a, past a pressing roll6a, to the outer surface of the roll formplate 1 and, passing around afeed-out roll 6b, is fed out. Clearance adjustments, etc., of both rollswith the roll formplate 1 are made possible.

The ionizing radiation curable resin 3 containing an abrasive materialis supplied from within the pan 4 by coating rolls 7 so as to fill atleast the plate concavities 5. Then, while the substrate 2 is contactingthe formplate 1, ionizing radiation rays R are irradiated toward thesubstrate 2 by an ionizing radiation irradiating device 8 thereby curingthe above mentioned resin 3 interposed between the substrate 2 and theformplate 1 and simultaneously causing the same to adhere securely tothe side of the substrate 2. Finally, at a feed-out roll 6b, thesubstrate 2 is peeled off from the formplate 1.

By thus peeling the substrate 2 off from the formplate 1, an abrasivetape 11 having on the substrate 2 a polishing abrasive layer 10 providedwith recesses 9 formed by the roll formplate 1 as shown in FIG. 2 isobtained. According to this invention, since the forming of the layer 10having the recesses 9 is carried out by a production method as describedabove, sharp and clear shapes of the recesses 9 that are faithfulreproductions of the shapes profiled on the roll formplate 1 areobtained. Particularly, even in the case where the recesses are ofcomplex and delicate shapes, they can be obtained simply and positively.

According to this invention, furthermore, by so feeding a substrate 2provided on one surface thereof with the abrasive layer 10 that theother surface thereof, i.e., the surface with no polishing layer formedthereon, contacts the roll formplate 1 and passing the same through thesame production process as that described above, abrasive layers 10 ofthe same kind can be formed on both surfaces of the substrate. In thecase where abrasive layers 10 are to be provided on both surfaces of thesubstrate, furthermore, by installing a second roll formplate on thedownstream side in the feed direction of the substrate, and feeding thesubstrate 2 after it has been peeled off from the first roll formplatedirectly, as it is, to the second roll formplate, continuous productioncan be carried out.

As shown in FIG. 3, the abrasive polishing layer 10 of the instantexample is of a configuration in which a resin layer part 9a of thepolishing layer exists at the bottom of each recess 9. Thisconfiguration is so formed that the ionizing radiation curable resin 3supplied to the plate concavities 5 of the roll formplate 1 will notonly be supplied into the plate concavities 5 but will also beinterposed between the peripheral surface of the formplate 1 and thesubstrate 2. In the case where an abrasive layer 10 of a configurationwherein a resin layer part 9a does not exist at the lower part of eachrecess 9 is to be obtained, a procedure such as scraping away with adoctor blade (not shown) the resin 3 on the formplate surfaces otherthan the plate concavities 5 is carried out after the resin 3 has beensupplied to the roll formplate 1 thereby to carry out adjustment so asto fill only the plate concavities 5 with the curable resin 3.Incidentally, as shown in FIGS. 2 and 3, the recesses 9 are partitionedby banks 9b encompassing the recesses.

The forming of the plate concavities 5 in the roll formplate 1 can becarried out by a method such as electronic engraving, etching, machiningon a lathe, milling machine, or the like, electroforming, andsand-blasting. Furthermore, the shape of each plate concavity 5 is acomplementary shape of the shape of each recess 9 of the polishinglayer, and in actuality, the convex-shaped parts impart recessed shapes.The recesses in the abrasive tape according to this invention carry outthe function of accommodating and thereby collecting the polishingdebris produced from the workpiece during polishing. In order to makepossible efficient accommodation of this polishing debris, it isdesirable that the recess 9, in general, have an opening width of 0.1 to200 μm, a depth of 0.1 to 100 μm, and a pitch (spacing of the centerparts of adjacent recesses) of 10 to 500 μm. The capability ofaccommodating polishing debris in recesses which do not satisfysimultaneously these dimension conditions becomes inadequate. Accordingto this invention, however, the forming of recesses of conditions otherthan those recited above is of course possible. Furthermore, therecesses 9 are arranged uniformly and regularly over the entire surfaceof the abrasive layer 10 as illustrated by one example in FIG. 3. Inaddition, the recesses can be so formed that the shape of each in planarview (in horizontal section) is quadrilateral, hexagonal, circular,elliptical, or some other shape and in vertical section is the shape ofan inverted triangle, a rectangle, a semicircle, a trapezoid, or someother figure. That is, the plate concavities 5 are provided with a shapesuch as to form recesses possessing simultaneously various structuralrequirements as described above.

For the above mentioned ionizing radiation curable resin, known resinsof the type which are cured by irradiation with ultraviolet rays or anelectron beam can be used. When, among these (resins), a resin of thetype to which no solvent is added is used, undesirable results such asvolumetric contraction, deformation, and generation of bubbles due tosetting do not occur, and, in addition to a process step of predryingthis resin becoming unnecessary, it becomes easier to obtain positivelyrecesses of good reproducibility. Furthermore, among the ionizingradiation rays, ultraviolet rays can be used in the case where the filmsubstrate 2 is transparent. However, in the case where the substrate isopaque, it is necessary to use an electron beam. Furthermore, if theroll formplate is constructed of a material through which ionizingradiation rays can be transmitted, irradiation from an irradiatingdevice installed in the interior of this formplate will become possible.In the case where an electron beam is used, the quantity of irradiationthereof depends on factors such as the thickness and material of thesheet substrate, but ordinarily (an irradiation quantity of) the orderof 0.5 to 30 Mrad is desirable.

The shape of the recesses is so designed that, in addition to therequirement for polishing performance of the polishing adhesive layer,the recesses will fulfill also the requirement of suitability forseparating of the polishing layer from the roll formplate together withthe film substrate. Specifically, a suitable shape of the plateconcavities on the roll formplate is such that, as shown in FIGS. 4 and5, the sectional area of each plate concavity 5 cut by the horizontalsectional plane indicated by line X--X becomes smaller progressively andcontinuously towards the bottom thereof. For example, when sand-blastingis carried out on a metal plate, a shape of a recess as shown in FIG. 4is obtained. Furthermore, plate concavities 5 of the shape shown in FIG.4 can be formed also by forming cells which have been demarcated byhalftone dots or multiline screen, etc., through the use of a plateproducing method depending on etching of known gravure printing process,during which the widths of the convex parts are made appropriatelynarrow, and, moreover, amply promoting the side etching of the cellinner walls thereby to remove the portions immediately below the resist.

In addition, plate concavities 5 of a shape as shown in FIG. 4 can alsobe formed by the aforedescribed machining, and plate concavities 5 ofthe shape shown in FIG. 4 can also be formed by forming concavities bythe aforedescribed etching method and thereafter carrying outsand-blasting.

Plate concavities 5 of the shape shown in FIG. 4 can be formed by knownphotoetching (or photolithographic) methods other than theaforedescribed gravure plate processing method. That is, it is alsopossible to: lay a photosensitive resist film 16 on a surface of a metalplate 15 as shown in FIG. 6; next, through an original plate (photomask)having the desired concavity shape (whether to be used as a negative orwhether to be used as a positive of the concave part pattern, selectionis made according to whether the resist is of the negative type orwhether it is of the positive type), expose the resist film 16 to lightto develop the same; open windows 18 of the desired shape of openingpart by leaving a resist pattern 16a; etch the metal within the windows18 as indicated at 20 in FIG. 7 with a suitable etching solution 19 suchas an aqueous solution of ferric chloride (Fe₂ Cl₃); thereafter causeside etching with the etching solution in the concave parts 20 asindicated at 21 in FIG. 8; and cause side etching to proceed further,whereby, through the state indicated in FIG. 9, plate concavities 5 asshown in FIG. 10 are obtained.

In this operation, however, care must be exercised in controlling thedegree of side etching. That is, by restricting the degree of sideetching, the forming of the concavities is stopped in the state as shownin FIG. 7. Alternatively, by permitting the side etching to proceedamply, the banks between the concavities are destroyed as indicated inFIG. 9 thereby to obtain the state indicated in FIG. 10.

The necessity of peeling the substrate 2 having the polishing layer 10from the roll formplate 1 as indicated in FIG. 1 has already beenmentioned. The polishing layer (cured resin layer) can be so formed thatit can be peeled off from the formplate and have concavities in whichside etching is negligible as shown in FIG. 7 in the following manner.For the roll formplate, a copper cylinder is used. An aqueous solutionof ferric chloride (of a concentration of 39 to 42 Baume degrees asmeasured with a Baume hydrometer) is used for the etching solution. Thisetching solution is supplied onto the copper surface by a shower methodor an air-agitation method. In the case where carbon tissue (potashgelatin dichromate) used in ordinary gravure processing is used for theresist film, the depth of the plate concavities is made less than 150μm. By this process, plate concavities in which side etching has beensuppressed as shown in FIG. 7 are obtained. When the extent of the sideetching 21 shown in FIG. 8 is excessively great, the resin which hasfilled the plate concavities and has set cannot be easily dislodged fromthe plate concavities, and peeling off becomes difficult. However, bysatisfying the above described conditions, peeling off becomes possible.

As a condition for attaining simultaneously a compatible combination ofboth polishing performance and good separation property of the platefrom the mold, the cumulative frequency distribution curve (ogive) ofthe surface roughness of the roll formplate 1 is also important. Morespecifically, when the steps of: obtaining statistical data of theheights of the hills (concavities/convexities) of the surface of theroll formplate by means of a measuring and curve-plotting instrument forsurface roughness of an electric tactometric type, optical type, or thelike; and plotting cumulative frequency distribution function f (R)curves with surface roughness, that is, height of the hills, R, asabscissa and cumulative frequency distribution function of the surfaceroughness ##EQU1## (where P(R) is the probability density function ofthe surface roughness R) as ordinate are taken, curves as shown in FIG.11 are obtained. Then, even if the maximum value R_(max) is the same,the rise of the curve is gentle as in the curve f_(B) (R) in FIG. 11,and, in the case where it becomes a curve of downward convexity, themold separation of the formplate is good. According to this invention,as shown in FIG. 11, the design is carried out so as to obtain a curveof this character.

On the other hand, in the case where the rise of the curve is steep asin the curve f_(A) (R), and it becomes a curve of upward convexity, themold separation of the formplate becomes poor.

A specific example of the shape of the formplate surface in the case ofa function such as is indicated by curve f_(A) (R) is as shown in FIG.12. In the case of a function such as is indicated by curve f_(B) (R),the shape becomes as shown in FIG. 13, for example.

In the case of a shape wherein the sectional area of the plate concavity5 increases toward the bottom, as in FIG. 14, the polishing layer aftercuring cannot be separated from the mold. Such a shape is thereforeunsuitable for attaining the objects of this invention. An example ofsuch a shape is shown in FIG. 8, wherein side etching has been carriedout by the etching method as described hereinbefore. In addition, in thecase where a matte-plated surface comprising an aggregate of finelump-shaped (spherical) particles of a metal such as chromium isprovided on the formplate surface, the sectional shape becomes as shownin FIG. 14. Thus, the mold-separation characteristic becomes poor alsoin this case.

As was mentioned hereinbefore, in the case where, the cumulativefrequency distribution curve of the height of theconcavities/convexities is as indicated by curve f_(B) in FIG. 11, thatis, the curve has a downward convexity over the entire region from 0% to100% of the cumulative frequency, good mold separability results.However, even if there is a portion of upward convexity in one part ofthe cumulative frequency distribution curve, in the case where the pointat which the cumulative frequency distribution of the cumulativefrequency distribution curve becomes 50% (that is, the pointcorresponding to the average value) passes on the right-hand side of themiddle value of the height, that is, average value≧middle value, amplysatisfactory mold separability of the set resin layer from the formplatecan be obtained.

FIGS. 15 and 16 illustrate actual examples of such a case. As indicatedin FIGS. 15A and 16A, even if a distribution curve of downward convexityis obtained, the relationship of "average value≧middle value" of theconcavities/convexities height in these cases is satisfied, and theshapes of the concavities/convexities are respectively as shown in FIGS.15B and 16B. Thus the mold separabilities of the set resin layers fromthe formplate were good. In this connection, the section of theformplate surface of FIG. 15B was obtained by sand-blasting the surfaceof a smooth copper cylinder with #80 sand, and the section of theformplate surface of FIG. 16B was obtained by sand-blasting the surfaceof a smooth copper cylinder with #200 sand.

In the case shown in FIG. 17A, the average value is 52% of the maximumvalue, and moreover the cumulative frequency distribution curvecomprises a portion of downward convexity and a portion of upwardconvexity. In this case, although mold separation was possible, therewas some resistance to mold separation. This case indicates borderlineor threshold conditions of mold separability. FIG. 17B shows theformplate surface corresponding to FIG. 17A. This sectional shape wasobtained by lightly etching the surface of a smooth copper cylinder,sand-blasting this surface with #200 sand, and further plating thesurface with lustrous chromium plating as indicated at 1a.

FIG. 18A illustrates a case where the cumulative frequency distributionis linear. In this case, good mold separation was obtained. This is alsoa case of borderline conditions between f_(A) (R) and f_(B) (R) of FIG.11. FIG. 18B shows the formplate surface corresponding to FIG. 18A. Thisformplate surface was obtained by forming ridges of a section of aright-angled isosceles triangle on the surface of a smooth coppercylinder by means of a lathe.

FIG. 19A indicates a case wherein the cumulative frequency distributioncurve has a portion of upward convexity and a portion of downwardconvexity and a relationship of average value<middle value. The moldseparability in this case was poor. FIG. 19B shows the formplate surfacecorresponding to FIG. 19A. In this case, the surface of a smooth coppercylinder was plated with a plating layer 1b of a chromium matte(delustering particulate state).

FIG. 20A illustrates a case where the cumulative frequency distributioncurve becomes a curve of downward convexity over the entire scope ofconcavity/convexity height. The peeling characteristic from the rollformplate in this case was good. FIG. 20B shows the sectional shape ofthe formplate surface corresponding to FIG. 20A. This formplate surfaceshape was produced by carrying out molding from a polyethyleneterephthalate film obtained by kneading thereinto calcium carbonate ofparticle size of 1 to 10 μm and fabricating the plate by theelectroforming method.

In addition to the recessed parts or depressions of the polishing layer10 shown in FIG. 3, the examples thereof shown in FIGS. 21 to 25 arepossible.

In the polishing layer 10 shown in FIG. 21, the depressions are formedby grooves 9A, which are connected to form a pattern of hexagons, theentire assembly resembling a tortoise-shell. The grooves form hexagonallands (islands) 23. In the middle of each island, a recess 9B ofpin-hole shape is formed.

In the polishing layer 10 shown in FIG. 22, the depressions compriselinear grooves 9c mutually intersecting at substantially right angles.Square lands 24 are thus formed by these grooves 9c.

In the polishing layer 10 shown in FIG. 23, lands 25 of a convex curvedsurface shape such as a semisphere or semiellipsoid are formed insteadof the square lands 24 of the polishing layer of FIG. 22. Depressions 9dare provided around these lands 25.

In the abrasive polishing layer 10 shown in FIG. 24, a land 26 isfurther formed in the middle of each depression 9 in the polishing layerof FIG. 3.

In the polishing layer 10 shown in FIG. 25, parallel lands 27 ofcurvilinear ribbon form are formed by depressions 9e of curvilineargroove form lying therebetween. The curves of these curvilinear shapesare curves of bounded periodic functions such as a sinusoidal curve, ahyperbolic curve, an elliptic function curve, a Bessel function curve, acycloidal curve, or an involute curve.

In addition to those described above, the shape of concavities of thepolishing layer is suitably selected in accordance with conditions suchas the kind of workpiece to be polished, the degree of precision of thepolishing, and the object.

In general, in the case of use wherein the polishing quantity is largeand a large quantity of the polishing debris is discharged over a longperiod, a configuration as shown in FIGS. 21 and 22 wherein the volumeof the recessed parts for accommodating the polishing debris isrelatively large, and, moreover, the groove-shaped recesses extend tothe peripheral edge of the polishing layer is suitable.

In certain applications, such as polishing of magnetic recording mediumsand magnetic heads, the forming of smooth surfaces with high finishingprecision is required. In such a case, the working surface of thepolishing layer 10 may take a configuration wherein the recesses 9 aremutually isolated as in the examples shown in FIGS. 3 and 24.Furthermore, in order to attain a high uniformity of finish, it ispreferable that the angles formed by the edges of the recesses and thelands therebetween relative to the polishing direction be numerous andthat, moreover, the symmetry of the configuration thereof be good. Forexample, the configuration of the example shown in FIG. 21 is betterthan that shown in FIG. 24 for this purpose.

The dimensions of the various configurations of the polishing layersshown in FIGS. 21 through 25 are also selected suitably in accordancewith the application, the finishing precision, and the material of thearticle to be polished. In general, however, in the case where finishingprecision is required as in the polishing of articles such as magneticrecording mediums, the dimension of the recesses (the width in the caseof groove-shaped recesses; the length of one side of each recess in thecase of isolated polygonal recesses; and the diameter of each recess inthe case of isolated circular recesses), is ordinarily approximated 0.1to 200 μm and the depth of each recess is approximately 1 to 100 μm, asstated hereinbefore.

The forward relief angle α and the rearward relief angle β between thefront and rear parts of the land, i.e., the convexity, of the polishinglayer 10 and the workpiece 30 undergoing polishing, as shown in FIG. 26,are also selected at suitable values in accordance with factors such asthe application, the material of the workpiece 30, and the polishingspeed.

The relief angles α and β contribute to the performances of dischargingand intercepting the polishing debris. That is, as indicated in FIG. 27,the polishing debris 31 is discharged through the range of the reliefangles α and β and is intercepted and accumulated in recesses of thepolishing layer 10.

Furthermore, the relief angles α and β, together with the contact arearatio R of the polishing layer 10 relative to the workpiece 30,contribute to the polishing efficiency. The contact area ratio R can beexpressed by the following equation. ##EQU2## wherein: Sc is the area ofcontact between the polishing layer 10 and the workpiece 30; Sg is theprojected area of the portion of the polishing layer 10 that is not incontact with the surface of the workpiece (i.e., the portion with aspace gap therebetween) which area is projected onto the surface of thefilm substrate 2; Sp is the area of the flat portion of the top parts ofthe lands of the polishing layer 10; and Sr is the area of the otherportions (corresponding to the concave portions) projected onto thesurface of the film substrate 2.

The approximation of the furthest right side of the above equation iseffective in the case where the tops of the lands are flat as in FIGS.26 and 27. Each summation Σ is taken over an amply broad area of thepolishing layer 10. If the contact area ratio R becomes too small, theportion of the polishing layer 10 which is not used will increase. Onthe other hand, if the ratio R becomes too large, the capacity of thepolishing layer 10 to discharge/intercept the polishing debris 31 willdrop.

As described hereinbefore with respect to the example shown in FIG. 1,the plate concavities 5 of the roll copper plate 1 can be supplied andfilled with an ionizing radiation setting resin by a roll-coating methodwith the use of coating rolls 7. This supplying and filling process canbe carried out alternatively also by other methods. For example, thisprocess can be carried out by supplying the resin from a die such as a Tdie as described hereinafter. Another possible method comprises coatingand forming the resin by a method such as roll coating beforehand on thefilm substrate 2 before the substrate 2 contacts the roll formplate 1.

The resin can be applied as a coating on the surface of the filmsubstrate 2 in the following manner. As shown in FIG. 28, the filmsubstrate 2 stock is supplied from a supply roll 2a to a roll-coatingsection 36 comprising guide rolls 32 and 33, pressing roll 34, and acoating roll 35 as essential parts. In this roll-coating section 36, theionizing radiation curable resin 3 in liquid form is applied as acoating on the substrate 2 thus supplied. Next, in the case where theresin 3 contains a diluting solvent, the substrate 2 is passed through adrying device 37, where the dilute solvent is evaporated off by a methodsuch blowing warm air. Thereafter, by means of a pressing roll 6a, thecoated surface of the film substrate 2 is pressed into contact with thesurface of the roll formplate 1. A portion of the coated resin layer 3is thereby forced to fill the interior of the plate concavities 5.Reference numerals 38 and 39 designate a liquid accumulation and an inkpan, respectively. In addition to roll coating, this coating process canbe accomplished by suitably applying any of various methods such asgravure roll coating and flow coating.

The resin liquid can be applied onto the surface of the roll formplatealso by another method as follows. As shown in FIG. 29, as the rollformplate 1 is rotated, liquid resin 3 is ejected through a T-dye typenozzle 41 and applied on the surface of the formplate 1. Thus the resin3 is caused to fill the interiors of the plate concavities 5.Separately, but simultaneously, uncoated film substrate 2 is supplied inthe arrow direction and is pressed into forceful contact with the coatedsurface of the roll formplate 1 by a pressing roll 6a. FIG. 30 is a viewfrom the left side of FIG. 29. In this connection, it is possible to usealso another method of coating the surface of the formplate 1. Oneexample of an alternative method is dipping of the roll formplate 1directly in the liquid resin in an ink pan.

In any of the above cases, it is important to prevent the mixing of airbubbles into the resin between the film substrate 2 and the surface ofthe roll formplate 1. A specific preventive measure for this purpose isas follows. As shown in FIGS. 29 and 30, surplus resin liquid 3 issupplied beforehand through the nozzle 41. Then, surplus resin liquid issqueezed out by rubbing action due to the compression by the pressingroll 6a, thereby to form a liquid accumulation 42. As a result, air isalso squeezed out by the rubbing action.

When the above two methods are compared, the method of coating onto theside of the film substrate 2 as indicated in FIG. 28 is preferable inthe case where the depth of the plate concavities 5 of the rollformplate 1 is relatively shallow, and where the fluidity of the resinliquid is also good, or where a dilute solvent is used.

Still another case where the method of coating onto the film substrateside of FIG. 28 is suitable is the case where, as a consequence of theaddition of the abrasive polishing material, the fluidity of theionizing radiation curable resin 3 becomes poor, and an increase in itsviscosity and thixotropy, dilatancy, and the like occur. Consequently,coating and supplying the resin cannot be carried out without dilutionof the solvent.

In this case, if coating were to be carried out directly on the surfaceof the roll formplate as shown in FIG. 29, drying of the solvent wouldbecome difficult. Accordingly, as indicated in FIG. 28, a resin solutionwhich has been amply diluted with the solvent is first applied as acoating on the film substrate to form a coating film of the desiredsurface smoothness. Thereafter, by means of a drying device, thediluting solvent is evaporated off. The coating film is then caused tocontact the roll formplate.

The reason for this procedure is that, if the solvent remaining as it isin residual state in the coating film were to be clamped and entrappedbetween the film substrate and the roll formplate, the residual solvent,being unable to escape, would remain as bubbles in the coating film. Asa consequence, there would arise the possibility of the shapes of thesurface concavities and convexities, the strength of the coating film,and the polishing performance being impaired. As a specific example, inthe case of quartz (silica) sand, solvent dilution becomes necessarywhen the quantity thereof added is 50 percent by weight or more.

On the other hand, when the concavities of the roll formplate arerelatively deep, and when the fluidity of the resin liquid is amplygood, the method of direct coating onto the formplate surface as shownin FIG. 29 is suitable.

According to the present invention, a roll formplate of a rigid materialsuch as a metal or glass is used. Furthermore, the film substrate ispressed by a pressing roll over the resin liquid, and moreover a tensionis applied to the film substrate.

For this reason, as shown in FIG. 31, the particles P of the polishingmaterial in the vicinity of the surface of the polishing layer 10 areblocked and prevented from protruding outward by the plate surface ofthe roll formplate 1. Furthermore, the resin liquid (binder), aided bythe pressing pressure, amply flows into and fills also the interfacebetween the polishing material particles or grains P and the platesurface. As a result, the surface of the polishing layer 10 after beingthus molded becomes a smooth surface as indicated in FIG. 32.

Of course, it is also possible to obtain a polishing layer 10 with asurface having concavities and convexities of the set resincorresponding to the polishing particles or grains P or a polishinglayer 10 with a portion where polishing particles or grains P have beenexposed directly at the surface as shown in FIG. 33. Such a polishinglayer 10 can be obtained by measures such as reducing the pressingpressure or the fluidity of the resin liquid or by selecting somewhathigh values of the curing shrinkage rate of the liquid of the resin 3 ofionizing radiation curing type. In comparison with the case illustratedin FIG. 32, that shown in FIG. 33 has a greater polishing capacity.

Even when the liquid of the same ionizing radiation curable resin isused, it is possible, depending on the method of curing, to cause theuneven shapes of the polishing particles P to emerge out of the surfaceof the set resin layer, as shown in FIG. 33, or furthermore to causeportions of the polishing particles P themselves to be directly exposedat the surface.

More specifically, in comparison with the method of curing withultraviolet rays, setting with an electron beam increases thecrosslinking density of the resin and increases the curing shrinkagerate. Therefore, even with the same resin liquid, when curing is carriedout with an electron beam, or when, after partial curing is first causedto proceed with ultraviolet rays, the remainder is cured with anelectron beam, a state resembling more closely that shown in FIG. 33 canbe obtained. In either of the cases illustrated in FIGS. 32 and 33, itis possible to prevent large protrusions of polishing particles outwardfrom the surface of the resin layer 10 as shown in FIG. 38 which hasoccurred with prior art methods.

One mode of practice of the preferred resin curing method according tothis invention is illustrated in FIGS. 28, 29, 34, 35, and 36. Asindicated, by a multistage curing process, the polishing particles orgrains in the polishing layer are caused to be more densely distributedin vicinity of the surface of the polishing layer. More specifically, asshown in FIGS. 28 and 29, a plural number of ionizing radiation devices8a, 8b, and 8c are installed at positions to confront and irradiate thesurface of the roll formplate 1, being spaced at suitable intervals inthe circumferential direction of the formplate 1.

In the setting process of the ionizing radiation curable resin liquid 3,the relationship between the total irradiation energy E required forcompletion of curing of N radiation devices 8a, 8b, 8c, . . . , 8N andthe irradiation energies E₁, E₂, E₃, . . . , E_(N) respectively thereofis as follows.

    E=E.sub.1 +E.sub.2,+E.sub.3 +. . . +E.sub.N

The irradiation of the ionizing radiation rays is carried outsuccessively in this order by dividing (E).

Ordinarily, the relationships between the respective energies of theradiation devices are approximately as follows.

    E.sub.1 ≈E.sub.2 ≈E.sub.3. . . ≈E.sub.N =E/N

However, the relative distribution of these energies E₁, E₂, E₃, . . . ,E_(N) is suitably adjusted in accordance with factors such as thedesired distribution of the polishing particles in the thicknessdirection of the polishing layer, the kind of resin to be set, and typeof irradiation.

The stages of an example of the multistage setting process of thischaracter are shown in FIGS. 34 through 37.

First, as indicated in FIG. 34, a film substrate 2 is pressed againstthe surface of the roll formplate 1 over the yet to be cured resinliquid 3 interposed therebetween. The resin liquid 3 is thereby coveredand caused to adhere intimately. Next, at the position confronted by thefirst ionizing radiation device 8a, ionizing radiation rays areprojected onto the coated film 3 (polishing layer 10). Thereupon, asindicated in FIG. 35, the resin 3 closer to the side of the filmsubstrate 2 sets. As a consequence, the distance between the moleculesin the resin liquid 3 in this region is narrowed by the cross-linkingreaction, and the resin 3 shrinks in volume. As a result, the polishingmaterial particles P, which had been dispersed, are squeezed out fromthe spaces between the molecules and migrate from the side of the filmsubstrate 2 toward the yet not cured resin on the formplate side.

Then, at the position confronted by the second radiation device 8b,radiation of the coated film 3 is continued. The resin nearer to filmsubstrate 2 thereby undergoes cross-linking and shrinks in volume asindicated in FIG. 36. Consequently, the polishing material particles Pmigrate further toward the direction of the formplate 1. Then, when thecoated film 3 is irradiated by the third radiation device 8c, thepolishing particles P are moved further toward the formplate (notshown). Thereafter, as the resin layer 3 thus cured (polishing layer 10)is separated from the surface of the formplate 1, an abrasive tape 11 inwhich the polishing particles P are distributed with even higher densityin the vicinity of the surface, as indicated in FIG. 37, is obtained.

Thus, by this method of curing by multistage ionizing radiation,particles added into a coated film are caused to rise to the surfacethereby to obtain a coated film in which the particles are distributedwith high density in the vicinity of the coated film surface. Thismethod per se has been previously disclosed in Japanese PatentPublication No. 58-15183 and Patent Application Laid-Open No. 2-261572.By the methods as thus disclosed previously, the coated film is cured infree air. Therefore, although the effect of causing the added particlesto rise is good, the particles could not be prevented from protrudingout through the surface of the coated film.

In contrast, by the method of this invention, the multistage setting ofthe resin is carried out with the surface of the coated film in a stateof being fixed to the surface of the formplate. For this reason, anexcellent polishing layer 10 as shown in FIG. 37 is obtained. Thus,protrusion of particles or grains outward through the surface due to thehigh density of the polishing particles in the vicinity of the surfaceas shown in FIG. 38 is prevented.

In some cases it is necessary to increase the cross-linking density atthe surface of the polishing layer and to increase the surface hardnessand resistance against heat and chemicals. This can be accomplished insuch cases by further irradiating with ionizing radiation rays theabrasive tape 11 from the polishing layer side after the tape 11 hasbeen separated from the roll formplate 1. More specifically, for exampleas indicated in FIG. 29, a back-up roller 43 and an ionizing radiationirradiation device 8d are provided on the downstream side of thefeed-out roll 6b. At this position, the abrasive tape 11 is in intimatecontact with the back-up roller 43 and is irradiated in wrapped state bythe irradiation device 8d.

A particularly effective method of increasing the cross-linking densityof the surface comprises, first, setting with ultraviolet rays thepolishing layer at the roll formplate surface and then, after separationfrom the formplate, irradiating the outer surface side of the polishinglayer with an electron beam. Although the mechanism of the action ofthis process is not yet clear, by carrying out irradiation with anelectron beam after curing with ultraviolet radiation, the hardness ofthe surface can be increased without overly lowering the calcinabilityof the entire resin layer.

However, if the irradiation is carried out excessively, the coated filmwill become fragile. As a consequence, when the abrasive tape is causedto assume a curve or is used in polishing, problems such as thedevelopment of cracks in the polishing layer and separation of thepolishing layer occur. For this reason, appropriate quantity ofirradiation and cross-linking density must be set.

Control of the temperatures of the roll formplate 1 and the back-uproller 43 is also important. In general, infrared rays are also radiatedfrom sources such as mercury lamps and carbon-arc lamps. Furthermore, inall cases where the ionizing radiation is by ultraviolet rays, anelectron beam, or the like, a part of the absorbed radiation energychanges into heat. Consequently, if this heating becomes excessive,defects such as deformation and heat deterioration will occur in thecured resin layer or film substrate. A measure for preventing this, inthe case of a mercury lamp or a carbon-arc lamp, is to insert a filterwhich transmits ultraviolet rays but shuts off infrared rays. In thecase where even this is insufficient, however, an effective measure isto cool the roll formplate itself. Since the resin coated film and thefilm substrate are both adhering intimately to the roll formplate, theheat generated in the coated film or the film substrate is rapidlyabsorbed by the roll formplate and cooled.

A specific example of practicing this method comprises using a rollformplate or/and back-up roller of hollow construction and passingcooling water through the interior thereof. In some cases, good resultsare obtained by heating the roll formplate or/and back-up roller to anappropriate temperature. This is a useful method for solving the problemof internal stress and/or residual strain remaining in the coated film(polishing layer) which has been cross-linked and cured by ionizingradiation.

In this case, a suitable surface temperature of the roll formplate andthe back-up roller is ordinarily of the order of 30° to 80° C. However,since heat generation accompanies ionizing irradiation, it is necessaryto take precautionary measures for preventing the temperature of theroll from rising above a limiting temperature with the passage of time.A specific measure is to use a hollow roll formplate and back-up rollerand to pass therethrough warm water at a specific temperature. By thismeasure, absorption of heat by the heat capacity of the water itself anddischarging of heating by the flow of the water are accomplished.

In the case where a plurality of ionizing radiation irradiating devicesas described hereinbefore are to be provided, an arrangement as shown inFIG. 39 is suitable. In this arrangement, two irradiating devices 8A and8B are provided around the roll formplate 1 at spaced apart positions.These spaced apart positions are such that the angle θ between the linesrespectively joining the two irradiating devices 8A and 8B to the centerO of the formplate 1 is 90 degrees. The points (lines) at which linesthat radiate from the irradiating device 8A and are tangent to the outersurface of the formplate 1 respectively at opposite sides thereof aredesignated A1 and A2. The points (lines) at which lines that radiatefrom the irradiating device 8B and are tangent to the outer surface ofthe formplate 1 respectively at opposite sides thereof are designated B1and B2. Then, in the case where a uniform irradiation intensity (W/m²)within the irradiated region A1-B1-A2-B2 on the circumferential surfaceof the roll formplate 1 is desired, portions of the irradiation regionsof the irradiating devices 8A and 8B are caused to overlap (as atB1-A2).

In the case where it is more desirable to provide a non-irradiatedregion between the region irradiated by the irradiating device 8A andthe region irradiated by the irradiating device 8B, the irradiationintensity of the arc B1-A2 is caused to be zero (0). This is a casewhere, for example, the internal stress of the polishing layer due toirradiation by the irradiating device 8A is once reduced, or thepolishing layer whose temperature has been raised is once cooled, andthereafter the remaining irradiation is carried out.

The quantity of ionizing radiation rays that have been irradiated can beused effectively without waste by either of the following methods. Inone method, the radiation rays emerging with maximum diverging anglefrom the irradiating devices 8A and 8B are caused to become tangents ofthe outer surface of the roll formplate 1 as shown in FIG. 39. In theother method, the irradiating devices are positioned even closer to theroll formplate 1. However, if they are brought excessively near the rollformplate, the irradiation quantity will become excessively great. Thiswill give rise to problems such as: deformation or cracking in the setcoated film due to rapid curing of the resin; and heat generation due toradiant heat unavoidably admixed with the radiation from the irradiatingdevices or due to conversion into thermal energy of the radiation raysin the coated film, this heat generation giving rise to a hightemperature rise in the coated film and thermal deterioration thereof.Therefore, the irradiating devices are kept at an appropriate distance.In this connection, for the purpose of coating the roll formplate, it isnecessary to leave at least 90/360 of whole circumference thereof as anon-irradiation region.

Advantages obtainable from the arrangement of FIG. 39 are as follows. Inthe prior art as disclosed in, for example, Japanese Patent Laid-OpenPubln. Nos. 2-131175 and 4-200766, only one irradiating device wasprovided. In such a case, as indicated in FIG. 40, the region ATB usedfor irradiation out of one circumference of the roll formplate 1 is alimited range. The irradiated region even at its maximum limit is up toone half of one circumference (as in the case shown in FIG. 41). In thiscase, the irradiating device is at an infinitely remote point, andfurthermore a parallel radiation flux of amply large area is used.

When, under these circumstances, an attempt is made to obtain amplesetting of the resin liquid, the total energy from the radiation sourceis concentrated in a small area. As a result, the unit irradiation(W/m²) becomes large, and, moreover, the total irradiation density(J/m²) is projected. As a consequence, the coated film rapidly sets, andstresses are not amply relieved. For this reason, development of strainand cracks in the coated film tend to occur. Furthermore, because ofradiant heat arriving in admixed state from the irradiation sourceand/or thermal energy arising from conversion into heat of a portionfrom the ionizing radiation rays within the coated film, the temperatureof the coated film rises to a high value, whereby heat deteriorationoccurs therein in some cases, and it is difficult to carry outsatisfactory setting of the coating film and forming of the concavitiesand convexities.

It may seem possible to solve the above described problems by increasingthe rotational speed of the roll formplate (travelling speed of the filmsubstrate). However, if the rotational speed is increased excessively,the action of the resin liquid in filling the interiors of theconcavities of the roll formplate and its displacing the air will nottake place satisfactorily. Furthermore, since the time period duringwhich any one part of the coated film is irradiated becomes shorter, theirradiation ends before cross-linking of the resin liquid orpolymerization reaction can occur completely, whereby defective settingof the coated film occurs in some cases.

On the other hand, by setting the angle θ between the centerlines of theradiation beams from the two irradiating devices 8A and 8B in thearrangement shown in FIG. 39 at 90 degrees, it becomes possible toobtain an irradiated region out of one circumference of the rollformplate which is twice as large as that in the case of one irradiatingdevice as shown in FIGS. 40 and 41. A maximum of 270/360 of the entirecircumference (a region of a central angle of 270 degrees) can beobtained as the irradiated area. (However, the ratio 270/360 is that forthe case where the irradiating device is infinitely remote (at a fardistance of an order which can be thus stated) or for the case where asurface irradiating device radiating a flux of parallel rays is used;ordinarily it is less.) For example, in the case of FIG. 39, 210/360 ofthe entire circumference becomes the irradiated region.

Of course, it is also possible to position three or more irradiatingdevices around the roll formplate and to carry out irradiation bysetting the angle between the lines joining adjacent two irradiatingdevices with the center of the roll formplate at less than 90 degrees.In such a case, it is also possible to obtain an irradiated region ofover 270/360 of the entire circumference.

However, ordinarily for the process of applying as coating the ionizingradiation curing type resin liquid on the roll formplate and fordisplacement of air by the resin liquid and filling of the concave parts(furthermore for drying of the solvent if the solvent dilution has beencarried out), a region of a minimum of the order of 90/360 of the entirecircumference is necessary. Furthermore, in view of the curing speed andquantity of irradiation necessary for curing of ordinary resins ofionizing radiation setting type in practical use at present, theirradiation output of the radiation source (principally ultraviolet raysor electron beam) and the like, two irradiation devices are ample. (Theirradiation quantity can be adjusted to some extent also by therotational speed of the roll formplate).

Accordingly, the optimum process is to use two irradiation sources and acenter angle formed thereby of 90 degrees. By this process, a largeirradiation region area of a maximum of 270/360 out of the entirecircumferential surface of the roll formplate required in practice canbe obtained. Moreover, by irradiating the irradiation quantity densitynecessary for the curing of resin liquid coated film over an amply longtime, deformation, cracking, or thermal deterioration of the coated filmdue to rapid curing can be prevented. In this connection, it ispossible, by adjusting the radiation angle of the irradiating deviceand/or the distance between the irradiating device and the rollformplate, to accomplish a substantially uniform irradiation over theentire region to be irradiated. Alternatively, it is also possible todivide the irradiation into two steps and to leave a region of restwithout irradiation. These possibilities can be suitably selected. Then,as described hereinbefore, in the region of 90/360 of the entirecircumference (region of 90° center angle) as a minimum, there exists aregion not reached by direct irradiation of the ionizing radiation rays.For this reason, there is little possibility of the supplied resin beingpartially or totally set by stray ionizing radiation rays prior to theforming of the resin by the roll formplate.

The polishing material or agent used in the present invention is notparticularly limited provided that it is one that is used for thepurpose of carrying out precision polishing. It can be selected from awide variety of materials according to the purpose of the polishingprocess. For example, in the case where the article to be polished ismade of a material of a high degree of hardness, such as an ultrahardtool, a polishing material such as green silicon carbide (SiC) ordiamond is suitable. For polishing articles of hard steels, specialsteels, high-speed steels, and the like, white fused alumina (Al₂ O₃) issuitable, while chromic oxide (Cr₂ O₃) is suitable for polishingarticles made of soft materials. For final polishing of magnetic heads,ferric oxide (Fe₂ O₃) is suitable. Polishing materials of a grain orparticle size of 0.1 to 20 μm are suitable.

Examples of other polishing materials are silicon nitride, zirconiumoxide, boron nitride, and emery. Furthermore, it is also possible to useparticles and flakes of synthetic resins as polishing materials.Examples of such resins are:

(1) Linear polyamides that are condensates of a diamine, NH₂ (CH₂)_(m)NH₂, and a dibasic acid, HOOC(CH₂)_(n-2) COOH, that is, m-n-nylon, morespecifically, 6-6-nylon wherein m=6 and n=6, 6-10-nylon wherein m=6 andn=10, etc.;

(2) linear polyamides that are polycondensates or polymers of ω-aminoacid, H₂ N(CH₂)_(n) COOH, or ##STR1## that is, n-nylon morespecifically, 6-nylon wherein n=6, 11-nylon wherein n=11, etc.;

(3) acrylic resins such as polyacrylates, e.g., polymethyl acrylate,polyethyl acrylate, and polybutyl acrylate, and polymethacrylates, e.g.,polymethyl methacrylate, polyethyl methacrylate, and polybutylmethacrylate.

(4) benzoguanamine

(5) melamine resin

Polishing materials produced from these synthetic resins are suitablefor polishing the surfaces of relatively soft articles such as syntheticresin products. Furthermore, such polishing materials can be used alsofor precision polishing requiring fine degrees of roughness.

In general, these synthetic resin polishing materials are superior tometals in their transmittances with respect to ultraviolet rays andvisible light rays. Furthermore, their indices of refraction are closeto those of ionizing radiation curable resins. For these reasons, theyare suitable for setting by radiation with ultraviolet rays and visiblelight rays.

As a desirable mode for preventing the abrasive polishing particles fromreadily peeling off during polishing and utilizing with maximumeffectiveness the hardness and polishing capability possessed originallyby the polishing particles, there is a method of coating the surfaces ofthe polishing material particles with a functional group having chemicalaffinity and good wettability with respect to the ionizing radiationcurable resin or causing chemical bonding thereof.

This method has already been disclosed in Japanese Patent PublicationNo. 16002/1993 as a process method with the object, in the production oflight-diffusing plates (or films) by dispersing particles of adelusterant or delustering agent in a transparent synthetic resin, ofobtaining uniformity of dispersion of the delusterant thereby to obtainuniformity of delustering and high light transmittance. In thedevelopment of this invention, it was found that this process method iseffective also for preventing peeling off of the polishing material andfor improving the polishing performance.

As a specific example, reference is made to Japanese Patent PublicationNo. 16002/1993, which discloses a process wherein, with the use ofparticles of a silicone resin (polysiloxane) comprising athree-dimensional-network high polymer as polishing (abrasive)particles, an alkyl group such as an ethyl group, a methyl group, apropyl group, or a butyl group, or an organic group such as a carboxylgroup, a carbonyl group, an ester group, or an ether group is caused tobond to at least silicon atoms in the vicinity of the outer surfaces ofthe silicon resin particles, thereby exposing a portion of the organicgroup at the surfaces of the silicone resin particles. The number ofthis organic group is desirably 0.5 or more and less than 1.5 per 1silicon atom. If this number is less than 0.5, the dispersibility andthe effect of preventing peeling with be inadequate. If it exceeds 1.5,the density of the mesh of the polysiloxane bond will become coarse, andthe capacity of the material as a polishing agent will be insufficient.

Another example of the above described method is that wherein a silanecoupling agent is applied as a coating on the surfaces of polishingparticles of silica, alumina, etc.

An even more desirable mode of procedure is that of dispersing, in anionizing radiation curable resin, particles obtained by subjecting thesurfaces of polishing material particles to a coating process with asilane coupling agent comprising alkoxysilane having aradical-polymerizable unsaturated group. This processing method also hasalready been disclosed in Japanese Patent Application Laid-Open Publn.No. 293099/1988 with the object stated therein of preventing blocking(preventing tackiness) of yet uncured coating film of resin of ionizingradiation curing type. According to the present invention, however, itwas discovered that the instant processing method is effective inpreventing the peeling off of the abrasive tape during polishing and inimproving the polishing performance thereof.

Specifically, the silane coupling agent is an alkoxysilane having aradical-polymerizable unsaturated group, such as for example,

γ-methacryloxypropyltrimethoxysilane,

γ-methacryloxypropylmethyldimethoxysilane,

γ-acryloxypropyltrimethoxysilane,

γ-acryloxypropylmethyldimethoxysilane,

and vinyltriethoxysilane.

As polishing materials for which processing with these (agents) isespecially effective, alumina (Al₂ O₃) and silica (SiO₂) can bementioned, but, of course, there is no reason for limitation thereof toonly these.

For coating processing a polishing material with the silane couplingagent, a method in which particles or grains of the polishing materialare dispersed in a solvent such as toluene, and thereafter a specificquantity of the silane coupling agent is added to cause a reaction isdesirable for carrying out the process uniformly.

When the polishing material particles thus processed are dispersed in asolution of the ionizing radiation curable resin and irradiated withionizing radiation rays, the radical polymerizable unsaturated group inthe silane coupling agent molecule cross links with a monomer,prepolymer, and/or oligomer in the solution of the ionizing radiationcurable resin, polymerizes, and chemically bonds to the polishingmaterial particles and the cured resin of the ionizing radiation curableresin, adhering strongly thereto.

Furthermore, depending on the use, it is also to use as the polishinglayer a material produced by forming desired irregularities ofconcavities and convexities on the surface of the cross-linked curedmaterial of the ionizing radiation curable resin solution without addingany polishing material whatsoever.

This polishing layer without a polishing material, also, is suitable forsurface polishing and precision polishing of soft substances such as,for example, synthetic resins.

The decisions as to whether or not to use a polishing material and tothe kind of the polishing material if used are suitably made inaccordance with factors such as the required polishing performance, thearticle to be polished, curing conditions, coating conditions, and thecase of forming the concavities and convexities.

In this connection, in the case where a polishing material is to beused, it is desirable that the content of the polishing material in thecoating for forming the polishing layer be 50 to 1,400 parts by weightrelative to 100 parts by weight of the binder component.

While the thickness of the polishing layer 10 is suitably set inaccordance with the use, a thickness of the order of 0.5 to 500 μm isordinarily suitable. Furthermore, in the case where the polishing layer10 is required to have a high flexibility or resistance to shrinkage,the requirement can be met by adding into the above mentioned curingtype resin a suitable quantity of a thermosetting resin such as, forexample, non-reactive acrylic resin or various waxes. In addition,additives such as an antistatic agent can also be added as necessary tothe polishing layer.

For the material of the polishing layer, a material containing as apredominant component a monomer, prepolymer, or oligomer having withinits molecule two or more ethylenically unsaturated groups such asacryloyl groups or methacrylol groups or thiol groups as a binder isused. Examples are acrylates such as urethane acrylate, polyesteracrylate, epoxy acrylate, trimethylolpropane triacrylate, anddipentaerythritol hexaacrylate; methacrylates such as urethanemethacrylate, polyester methacrylate, epoxy methacrylate,trimethylolpropane trimethacrylate, and dipentaerythritolhexamethacrylate; thiols such as trimethylolpropane trithiopropylate andpentaerythritol tetrathioglycol; and unsaturated polyesters.

Other than these, a monomer, prepolymer, or oligomer having one or moreof groups such as ethylenically unsaturated groups and thiol groupswithin the molecule can also be added. Examples are acrylates andmethacrylates. The cross-link density of the set substance and furtherphysical properties such as flexibility and heat resistance are adjustedby selecting the numbers of the functional groups, the molecularweights, the kinds, and other characteristics of the compounds to becompounded. In general, when a compound of a high molecular weight and asmall number of functional groups is made the predominant component, thehardness becomes lower, the flexibility increases, and the heatresistance decreases; whereas when a compound of low molecular weightand a large number of functional groups is made the predominantcomponent, the hardness becomes higher, the flexibility decreases, andthe heat resistance increases. In all cases, after crosslinking curing,macromolecules of three-dimensional network structure are formed.Furthermore, in order to improve the adhesivity relative to the filmsubstrate, a resin of non-crosslinked type such as a methacrylic resin,an acrylic resin, or a vinyl chloride-vinyl acetate copolymer can beadded.

In the case of crosslinking and curing with ultraviolet rays or visiblelight rays, an acetophenone, a benzophenone, or the like is added as aphotopolymerization initiator.

In general, in the case of a use for which a high degree of smoothnessof the finished surface is required as in the finishing of a magneticrecording material, a magnetic head, or the like, a good result isobtained by using a relatively soft (low degree of hardness) polishinglayer. As one criterion, it became clear as a result of experimentsthat, in the case of thermoplastic (saturated) polyester as the binderof the polishing layer, a substance of a glass transition point of 50°C. or lower, particularly 35° C. or lower, is desirable. The abovementioned hardness and flexibility of the set material of the ionizingradiation curable resin are also adjusted to an equivalent degree.

Specific examples are as follows.

An example of an ionizing radiation curing type resin solutioncomposition which will produce a crosslink cured substance that isrelatively flexible, pliant, yet tough is a composition obtained bymixing a substance having a hard segment and a soft segment in themonomer, prepolymer, or oligomer to become the polymerization unit. Uponbeing irradiated with ionizing radiation rays, these polymerizationunits mutually cross link and form a set substance. A specific exampleis a monomer, prepolymer, or oligomer of urethane acrylate. To this, foradjusting the crosslinking density and hardness of the set substance,acryl monomer is admixed.

For the above mentioned urethane acrylate, that of an average molecularweight of 500 to 50,000 is selected from those known heretofore.

As a specific example, an oligomer or a prepolymer of an urethaneacrylate having an urethane group and a radical polymerizableunsaturated group in the molecule can be obtained by causing anisocyanate having two or more isocyanate groups, a polyester prepolymerof a weight average molecular weight of 200 to 3,000 having 1 to 4hydroxyl groups in one molecule, and an acrylate compound having ahydroxyl group as a terminal group and moreover having a radicalpolymerizable unsaturated group to react in a solvent or not in asolvent in the presence of a reaction catalyst such as an amino or anorganic tin compound and a polymerization inhibitor such ashydroquinone.

As isocyanates for constituting the above mentioned urethane acrylate,there are aliphatic or aromatic isocyanate compounds. Examples areisophoronediisocyanate and hexamethylenediisocyanate.

Examples of the polyester prepolymer having 1 to 4 hydroxyl groups inone molecule which constitutes the above mentioned urethane acrylateare: addition reaction products of diol compounds having aromatic orspiro-ring skeletons and lactone compounds or derivatives thereof orepoxy compounds; condensation products of polybasic acids such asphthalic acid and polyols such as ethylene glycol; polyester diols suchas polyester compounds obtained by cleaving cyclic ester compounds;polyether diols such as polytetramethylene ether glycol, polyethyleneglycol, and polypropylene glycol; and polycarbonate diols. Thesecompounds are used singly or in a mixture of two or more members.

The weight average molecular weight of the polyester polymer having 1 to4 hydroxyl groups in one molecule is desirably within a range of 200 to3,000 from the standpoint of wear resistance and hardness, a range of500 to 1,500 being particularly desirable.

Examples of acrylate compounds having a hydroxyl group at the end ofeach molecule and, moreover, having one or more radical polymerizableunsaturated groups are hydroxylation derivatives of (meth)acrylic acidester such as hydroxyethyl acrylate and hydroxypropyl methacrylate andepoxy acrylate. Monomers of these (acrylates) are used.

In the case where a very high degree of smoothness of the finishedsurface is not required but, rather, it is necessary to increase thepolishing rate, the binder is made relatively hard. As a tentativecriterion, the hardness and flexibility are made to be of the same orderas those of a thermoplastic polyester of a Tg of 50° C. or higher.

In order to prevent generation of static electricity during polishing,an antistatic agent is added. In this case, it is desirable to devise ameasure for preventing the antistatic agent from migrating to the sideof the article being polished as the polishing proceeds.

For example, a good result can be obtained by causing a preparationresulting from the addition of a surface active agent (anionic ornonionic) molecule to a monomer, prepolymer, or oligomer having anethylenically unsaturated bond (acryloyl group, methacryloyl group, orthe like) to undergo crosslinking together with the aforementionedionizing radiation setting resin composition. An example of such asurface active agent is one having a structure represented by thefollowing formula (sold on the market under the trademark of "AdekareaSoap" from Asahi Denka Kogyo K.K., Japan). ##STR2## where X is H or SO₃NH₄.

The crosslinkable surface active agent undergoes crosslinking and curingtogether with the binder resin and, in the three-dimensional networkmacropolymer structure, chemically bonds by covalent bonding or thelike, thereby to form an integral structure. As an example of chemicalbonding of a surface active agent molecule to a three-dimensionalnetwork molecular structure formed by crosslinking or polymerization byionizing radiation rays, a composition as disclosed in Japanese PatentLaid-Open Publication No. Heisei 5-98049 may be used.

This is a composition of a resin of ultraviolet-ray setting typecomprising principally the following members (A), (B), (C), and (D) andused singly by itself or is a substance formed by dispersing particlesof the polishing material in said composition.

(A) A monomer having a quaternary ammonium salt represented by thegeneral formula ##STR3## where: R¹ represents a hydrogen atom or amethyl group; each of R³, R⁴, and R⁵ represents independently a hydrogenatom or an alkyl group; R² represents an alkylene group or anoxyalkylene group; and X⁻ represents a halogen ion, R⁶ SO³⁻ (R⁶ being analkyl group substituted aromatic group, alkoxy group), or (R⁷ O)₂ PO₂ ⁻(R⁷ being an alkyl group).

(B) A crosslinkable oligomer.

(C) A multifunctional acrylic ester and/or methacrylic ester of at leasttrifunctional character.

(D) A photopolymerization initiator.

As a separate example, graphite or metals such as, silver, copper,platinum, nickel, chromium, iron or ferrous alloys such as carbon steeland stainless steel, and aluminum or aluminum alloys such as duraluminin the form of powder or thin flakes are added to the polishing layer.In order to overcome problems such as impairment of the polishingcharacteristic and adherence to the article being polished, these (metalpowders or flakes) can be added to the film substrate material.

For the film substrate 2, any kind of film can be used as long as it hasbeen used from the past for polishing tapes and, moreover, has asuitable flexibility for its smooth passage of also rolls, etc., in theproduction process. For example, polyester film, polyethylene film,polypropylene film, polyvinyl chloride film, polyvinylidene chloridefilm, polycarbonate film, polyamide (nylon) film, polystyrene film,ethylene-vinyl acetate copolymer film, etc., can be used. Among these,when the points of ease of fabrication, strength, cost, etc., areconsidered, polyester films such as those of particularly biaxialorientated polyethylene terephthalate, polyethylene naphthalate, etc.,are desirable. The surfaces of these films to form the polishing layercan be processed according to necessity by corona discharge treatment orby easily adhesive primer treatment with polyester resin, etc.Furthermore, other than the above described substrates, depending on thenecessity, paper, fabric, non-woven fabric, synthetic paper, etc., whichhave been treated with a filler may be used. The thickness of thissubstrate 2 is desirably of the order of 12 to 100 μm. Further, thesesubstrates may be of a single layer or be laminated with two or morelayers.

According to the method of the present invention, an abrasive tape ofconstantly uniform and precise recessed part shape is obtained. At leastthe initial polishing capacity of this abrasive tape is stable.Furthermore, since the recessed parts are of specific shapes asdescribed hereinbefore, the polishing debris produced from the articlebeing polished during polishing is efficiently accommodated in theserecessed parts. As a result, there is little risk of damaging thesurface of the article being polished due to infiltration of polishingdebris in between the abrasive tape and the article being polished.Furthermore, there is also no lowering of the polishing capacity due toclogging of the pores of the polishing layer. The abrasive tape isparticularly optimally suitable for precision polishing such as thatrequiring mirror finishing. In addition, since the polishing layer isconstituted of an ionizing radiation curing type resin which has beenset, it has excellent physical properties such as wear resistance,whereby polishing by the polishing material is positively carried out,and there is little possibility of defective polishing of the articlebeing polished, polishing of high precision becoming possible.

Specific examples of practice of the present invention will now bedescribed.

EXAMPLE 1

On one surface of a polyester film (T-60, mfd. by Toray) of 25-μmthickness, a double-liquid curable type polyester primer was applied bythe gravure coating method so as to form a coating of a thickness of 0.3μm upon drying thereby to carry out mold release (lubrication)processing. On this thus-processed surface, a polishing layer was formedwith the following constituent materials and under the followingconditions by employing the production mode indicated in FIG. 1, therebyfabricating an abrasive tape.

Formplate--Use was made of a roll formplate with a concavity width of 10μm, a plate depth (depth of concavity) of 15 μm, and a concavity pitchof 30 μm. Moreover the planar shape was that of a tortoise-shell withplate concavities of rectangular cross section form.

Ionizing radiation curing type resin--A polyester-acrylate, electronbeam curing type paint containing 100 percent by weight of white fusedalumina was used.

Irradiation conditions--Irradiation was carried out with an electronbeam of 10×10⁶ rad by means of an electron beam radiating apparatus ofcurtain-beam type.

The abrasive tape thus obtained had a polishing layer with recessedparts formed in accordance with the plate, of desired sharp shape,moreover with good reproducibility. By using this polishing tape,polishing of stainless steel (SUS-45C, JIS) of a centerline averageroughness (JIS-B-0601, JIS) of 0.5 μm was carried out, whereupon apolishing finish of a centerline average roughness of 0.1 μm wasobtained. At the same time, furthermore, the polishing debris wasaccommodated in the above mentioned recessed parts, and damaging(scoring, abrading, etc.) of the surface of the article being polisheddid not occur.

EXAMPLE 2

On one surface of a biaxially oriented polyester film (T-60, mfd. byToray Kabushiki Kaisha) of 25-μm thickness, a double-liquid curing typepolyester primer was applied by the gravure coating method so as to forma coating of a thickness of 0.3 μm upon drying thereby to carry out moldrelease (lubrication) processing. On this thus-processed surface, apolishing layer was formed with the following constituent materials andunder the following conditions by employing the production modeindicated in FIG. 29, thus fabricating an abrasive tape.

Shape--A Bernard cell shape as shown in FIG. 21 was used.

Formplate--Use was made of a roll formplate with tortoise-shell shapegrooved concavities of a width of 5 μm, plate depth (cell depth) of 10μm, a diameter of 5 μm and depth of 3 μm of each pinhole in the centerof each region divided by the tortoise-shell shape grooved concavities,and a surface form comprising a reversal of concavities and convexitieswith a pitch of tortoise-shell grooves of 100 μm. The material compriseda hollow iron cylinder and a copper-plated layer on the outer surfacethereof, the concave-convex surface form being formed thereon.

Ionizing radiation curing type resin--An electron beam curing type paintcomprising 600 parts by weight of alumina powder (WA-#8000, mfd. byFujimi Kenmazai Kabushiki Kaisha) and 100 parts by weight of amultifunctional urethane acrylate prepolymer was used.

Irradiation conditions--Irradiation was carried out with an electronbeam of 10×10⁶ rad by means of an electron beam radiating apparatus ofcurtain-beam type. The interior hollow part of the roll formplate waswater-cooled to maintain the outer surface temperature at 20° C.

The abrasive tape thus obtained had a polishing layer having recessedparts formed in accordance with the plate, of desired sharp shape,moreover with good reproducibility. By using this abrasive tape,polishing of the surface of a 5.25-inch magnetic floppy disc of acenterline average roughness of 0.5 μm was carried out, whereupon apolishing finish of a centerline average roughness of 0.05 μm wasobtained. Furthermore, the polishing debris at this time wasaccommodated in the above mentioned recessed parts, and damaging of thesurface of the article being polished due to the polishing debris didnot occur.

EXAMPLE 3

On one surface of a biaxially-oriented polyester film (T-60, mfd. byToray) of 25-μm thickness, a double-liquid curing type polyester primerwas applied by the gravure coating so as to form a coating of athickness of 0.3 μm upon drying thereby to carry out mold releaseprocessing. On this thus-processed surface, a polishing layer was formedwith the following constituent materials and under the followingconditions by employing the production mode indicated in FIG. 1, thusfabricating an abrasive tape.

Formplate--For the shape, a Bernard cell shape as shown in FIG. 21 wasused. Use was made of a roll formplate with tortoise-shell shapedgrooved concavities of a width of 1 μm, plate depth (concavity depth) of2 μm, a diameter of 1 μm and depth of 1 μm of each pinhole in the centerof each region divided by the tortoise-shell shape grooved concavities,and a surface form comprising a reversal of concavities and convexitieswith a pitch of tortoise-shell grooves of 80 μm. The material was thesame as that in Example 2.

Ionizing radiation curing type resin--An electron beam curing type paintcomprising 600 parts by weight of alumina powder (WA-#8000, mfd. byFujimi Kenmazai Kabushiki Kaisha) and 100 parts by weight of amultifunctional urethane acrylate prepolymer was used.

Irradiation conditions--Irradiation was carried out with an electronbeam of 10×10⁶ rad by means of an electron beam radiating apparatus ofcurtain-beam type.

The abrasive tape thus obtained had a polishing layer having recessedparts formed in accordance with the plate, of desired sharp shape,moreover with good reproducibility. By using this polishing tape,polishing of the surface of a 5.25-inch magnetic floppy disc of acenterline average roughness of 0.40 μm was carried out, whereupon apolishing finish of a centerline average roughness of 0.09 μm wasobtained. Furthermore, the polishing debris at this time wasaccommodated in the above mentioned recessed parts, and damaging of thesurface of the article being polished due to the polishing debris didnot occur.

INDUSTRIAL APPLICABILITY

The present invention is applicable to polishing for the purpose of highprecision finishing of surfaces of articles such as floppy discs andmagnetic heads and end faces of optical fibers.

We claim:
 1. An abrasive tape comprising:a film substrate; a polishinglayer laminated on one surface of said film substrate and having anouter surface provided with a plurality of mutually isolated, adjacentrecessed parts, said polishing layer consisting essentially of anionizing radiation curable resin in the cured state.
 2. An abrasive tapeaccording to claim 1, wherein said polishing layer has athree-dimensional network molecular structure in which surface-activeagent molecules are chemically bonded.